Put the basil and garlic in small food processor and pulse until finely chopped. With the machine running, add the oil in a slow stream until completely emulsified. Transfer to an airtight container and store refrigerated until ready to use or freeze for up to one month.,______,Preheat the oven to 425°F.,Put the water and salt in a large saucepan. Bring to a boil over high heat. Add the barley, cover and cook on low heat until tender, about 45 minutes.,While the barley is cooking, heat 3 tablespoons of the olive oil, the butter, garlic and crushed red pepper in a large, ovenproof skillet over medium-high heat. Add the cauliflower and stir to coat the cauliflower evenly with the olive oil mixture. Cook for 1 to 2 minutes then transfer to the oven. Cook until browned and tender, about 20 minutes.,Whisk together the balsamic vinegar and mustard in a large bowl. Add the olive oil in a steady stream while continuing to whisk. Stir in the barley, cauliflower (including any bits of garlic or pepper stuck to the skillet), Parmigiano and celery leaves. Season to taste with salt and pepper. Sprinkle the croutons over the top and serve immediately.